Sciatic Nerve
Anatomy
- Exits the pelvis anterior and inferior to the piriformis via the greater sciatic foramen and then descends posterior to the femur.
- At the inferior femur, it divides into:
- The tibial nerve, which continues down the posterior tibia to innervate the posterior leg and plantar foot.
- The peroneal nerve, which wraps around the fibular neck and innervates the anterior and lateral leg and dorsal foot.
Innervation
- The sciatic nerve innervates the hamstrings muscles, which are semimembranosus, semitendinosus, and the short and long heads of the biceps femoris muscle.
- The peroneal division of the sciatic nerve innervates the short head of the biceps femoris.
- The peroneal innervation of the short head of the biceps femoris is especially important in localization because a peroneal neuropathy at the fibular head (the most common peroneal nerve entrapment site) will spare the short head of the biceps femoris.
- The tibial division innervates the other hamstrings muscles: the long head of biceps femoris, semitendinosus, and semimembranosus.
- The sciatic nerve's innervation to the adductor magnus muscle is supplied by L4, L5.
- The hamstrings and adductor magnus provide knee flexion and hip extension.